Multifunctional copolymer and lubricating oil composition

ABSTRACT

An additive composition comprising a graft and derivatized copolymer prepared from ethylene and at least one (C 3  -C 10 ) alpha-monoolefin and, optionally, a polyene selected from non-conjugated dienes and trienes comprising from about 15 to 80 mole percent of ethylene, from about 20 to 85 mole percent of said (C 3  -C 10 ) alpha-monoolefin and from about 0 to 15 mole percent of said polyene having an average molecular weight ranging from about 5,000 to 500,000, which has been reacted with at least one olefinic carboxylic acid acylating agent to form one or more acylating reaction intermediates characterized by having a carboxylic acid acylating function within their structure and reacting said reaction intermediate with an amino-aromatic compound to form said graft derivatized copolymer, and a lubricating oil composition containing same are provided.

This application is a continuation of application Ser. No. 07/939,744,filed Sep. 2, 1992 now abandoned.

BACKGROUND OF THE INVENTION

This invention relates to a novel multifunctional lubricant additivewhich is a VI improver, a dispersant, and an antioxidant additive whenemployed in a lubricating oil composition.

DISCLOSURE STATEMENT

The art contains many disclosures on the use of polymer additives inlubricating oil compositions. Ethylene-propylene copolymers andethylene-alpha olefin non-conjugated diene terpolymers which have beenfurther derivatized to provide multifunctional properties in lubricatingoil compositions illustrate this type of oil additive.

U.S. Pat. No. 4,089,794 discloses ethylene copolymers derived fromethylene and one or more (C₃ -C₂₈) alpha-olefins grafted with anethylenically unsaturated carboxylic acid material followed by areaction with a polyfunctional material reactive with carboxyl groups,such as a polyamine, a polyol, or a hydroxyamine which reaction productis useful as a sludge and varnish control additive in lubricating oils.

U.S. Pat. No. 4,137,185 discloses a stabilized imide graft of anethylene copolymer additive for lubricants.

U.S. Pat. No. 4,146,489 discloses a graft copolymer where the backbonepolymer is an oil-soluble ethylene-propylene copolymer or anethylene-propylene-diene modified terpolymer with a graft monomer ofN-vinyl-pyridine or N-vinylpyrrolidone to provide a dispersant VIimprover for lubricating oils.

U.S. Pat. No. 4,320,019 discloses a multipurpose lubricating additiveprepared by the reaction of an interpolymer of ethylene and a (C₃ -C₈)alpha-monoolefin with an olefinic carboxylic acid acylating agent toform an acylating reaction intermediate which is then reacted with anamine.

U.S. Pat. No. 4,340,689 discloses a process for grafting a functionalorganic group onto an ethylene copolymer or an ethylene-propylene-dieneterpolymer.

U.S. Pat. No. 4,357,250 discloses a reaction product of a copolymer andan olefin carboxylic acid via the "ene" reaction followed by a reactionwith a monoamine polyamine mixture.

U.S. Pat. No. 4,382,007 discloses a dispersant-VI improver prepared byreacting a polyamine-derived dispersant with an oxidizedethylene-propylene polymer or an ethylene-propylene diene terpolymer.

U.S. Pat. No. 4,144,181 discloses polymer additives for fuels andlubricants comprising a grafted ethylene copolymer reacted with apolyamine, polyol or hydroxyamine and finally reacted with an alkarylsulfonic acid.

The disclosures in the foregoing patents which relate to VI improversand dispersants for lubricating oils; namely, U.S. Pat. Nos. 4,089,794,4,137,185, 4,144,181, 4,146,489, 4,320,019, 4,340,689, 4,357,250, and4,382,007 are incorporated herein by reference.

An object of this invention is to provide a novel derivatized graftcopolymer composition. Another object of the invention is to provide amulti-functional lubricant additive effective for imparting viscosityindex, dispersancy, and antioxidant properties to a lubricating oilcomposition.

A further object is to provide a novel lubricating oil compositioncontaining the graft copolymer additive of the invention, as well as toprovide concentrates of the novel additive of invention.

SUMMARY OF THE INVENTION

The novel reaction product of the invention comprises a copolymer orterpolymer of a (C₃ -C₁₀) alpha-monoolefin, ethylene, and optionally, anon-conjugated diene or triene on which has been grafted anethylenically unsaturated carboxylic function which is then furtherderivatized with an amino-aromatic compound such as nitrophenylphenylenediamine represented by the formula ##STR1## wherein R¹ is--NH₂, --CH₂ --(CH₂)n--NH₂, --CH₂ -aryl-NH₂ in which n has a value from1 to 10, R₂ is hydrogen or a nitro group, and R³ is hydrogen or a nitrogroup.

The novel lubricant of the invention comprises an oil of lubricatingviscosity and an effective dispersant, viscosity index improving, andantioxidant amount of the novel reaction product of the invention.Concentrates of the reaction product of the invention are alsocontemplated.

DETAILED DESCRIPTION OF THE INVENTION

The polymer or copolymer substrate employed in the novel additive of theinvention may be prepared from ethylene and propylene or it may beprepared from ethylene and a higher olefin within the range of (C₃ -C₁₀)alpha-monoolefins.

More complex polymer substrates, often designated as interpolymers, maybe prepared using a third component. The third component generally usedto prepare an interpolymer substrate is a polyene monomer selected fromnon-conjugated dienes and trienes. The non-conjugated diene component isone having from 5 to 14 carbon atoms in the chain. Preferably, the dienemonomer is characterized by the presence of a vinyl group in itsstructure and can include cyclic and bicyclo compounds. Representativedienes include 1,4-hexadiene, 1,4-cyclohexadiene, dicyclopentadiene,5-ethylidene-2-norbornene, 5-methylene-2-norbornene, 1,5-heptadiene, and1,6-octadiene. A mixture of more than one diene can be used in thepreparation of the interpolymer. A preferred non-conjugated diene forpreparing a terpolymer or interpolymer substrate is 1,4-hexadiene.

The triene component will have at least two non-conjugated double bonds,and up to about 30 carbon atoms in the chain. Typical trienes useful inpreparing the interpolymer of the invention are1-isopropylidene-3,4,7,7a-tetrahydroindene, 1-isopropylidenedicyclopentadiene, and2-(2-methylene-4-methyl-3-pentenyl)[2.2.1]bicyclo-5-heptene.

The polymerization reaction to form the polymer substrate may be carriedout in the presence of a catalyst in a solvent medium. Thepolymerization solvent may be any suitable inert organic solvent that isliquid under reaction conditions for solution polymerization ofmonoolefins which is generally conducted in the presence of a Zieglertype catalyst. Examples of satisfactory hydrocarbon solvents includestraight chain paraffins having from 5 to 8 carbon atoms, with hexanebeing preferred. Aromatic hydrocarbons, preferably aromatic hydrocarbonshaving a single benzene nucleus such as benzene, toluene and the like;and saturated cyclic hydrocarbons having boiling point rangesapproximating those of the straight chain paraffinic hydrocarbons andaromatic hydrocarbons described above, are particularly suitable. Thesolvent selected may be a mixture of one or more of the foregoinghydrocarbons or a suitable oil base stock. It is desirable that thesolvent be free of substances that will interfere with a Zieglerpolymerization reaction.

In a typical preparation of a polymer substrate, hexane is firstintroduced into a reactor and the temperature in the reactor is raisedmoderately to about 30° C. Dry propylene is fed to the reactor until thepressure reaches about 40-45 inches of mercury. The pressure is thenincreased to about 60 inches of mercury by feeding dry ethylene and5-ethylidene-2-norbornene to the reactor. The monomer feeds are stoppedand a mixture of aluminum sesquichloride and vanadium oxytrichloride isadded to initiate the polymerization reaction. Completion of thepolymerization reaction is evidenced by a drop in the pressure in thereactor.

The present invention relates to a derivatized graft copolymer which isprepared from:

a polymer prepared from ethylene and at least one (C₃ -C₁₀)alpha-monoolefin and, optionally, a polyene selected from non-conjugateddienes and trienes comprising from about 15 to 80 mole percent ofethylene, from about 20 to 85 mole percent of said (C₃ -C₁₀)alpha-monoolefin, and from about 0 to 15 mole percent of said polyeneand having a number average molecular weight ranging from about 5,000 to500,000.

Ethylene-propylene or higher alpha-monoolefin copolymers may consist offrom about 25 to 55 mole percent ethylene and from about 45 to 75 molepercent propylene or higher alpha monoolefin with the preferred moleratios being from about 25 to 75 mole percent ethylene and from about 25to 75 mole percent of a C₃ -C₁₀ alpha monoolefin with the most preferredproportions being from 50 to 80 mole percent ethylene and 20 to 50 molepercent propylene.

Terpolymer variations of the foregoing polymers may contain from about 0to 15 mole percent of polyene with the preferred mole ratio being 0.1 to10 mole percent of a non-conjugated diene or triene. The polymersubstrate, that is, the ethylene copolymer or terpolymer, is anoil-soluble, substantially linear, rubbery material broadly having anumber average molecular weight from about 5,000 to 500,000, with apreferred molecular weight range of 25,000 to 250,000, and a mostpreferred range being from 50,000 to 150,000.

The terms polymer and copolymer are used generically to encompassethylene copolymers, terpolymers or interpolymers. These materials maycontain minor amounts of other olefinic monomers so long as their basiccharacteristics are not materially changed.

An ethylenically unsaturated carboxylic acid material is next graftedonto the prescribed polymer backbone. These materials which are attachedto the polymer contain at least one ethylenic bond and at least one,preferably two, carboxylic acid or its anhydride groups or a polar groupwhich is convertible into said carboxyl groups by oxidation orhydrolysis. Maleic anhydride or a derivative thereof is preferred. Itgrafts onto the ethylene copolymer or terpolymer to give two carboxylicacid functionalities. Examples of additional unsaturated carboxylicmaterials include chloromaleic anhydride, itaconic anhydride, or thecorresponding dicarboxylic acids, such as maleic acid, fumaric acid andtheir monoesters.

The ethylenically unsaturated carboxylic acid material may be graftedonto the polymer backbone in a number of ways. It may be grafted ontothe backbone by a thermal process known as the "ene" process or bygrafting in solution or in solid form using a radical initiator. Thefree-radical induced grafting of ethylenically unsaturated carboxylicacid materials in solvents, such as benzene, is a preferred method. Itis carried out at an elevated temperature in the range of about 100° C.to 250° C., preferably 120° C. to 190° C. and more preferably at 150° C.to 180° C., e.g., about 160° C., in a solvent, preferably a minerallubricating oil solution containing, e.g., 1 to 50, preferably 5 to 30weight percent, based on the initial total oil solution, of the ethylenepolymer and preferably under an inert environment.

The free-radical initiators which may be used are peroxides,hydroperoxides, and azo compounds, and preferably those which have aboiling point greater than about 100° C. and decompose thermally withinthe grafting temperature range to provide free radicals. Representativeof these free-radical initiators are azobis-isobutyronitrile and5-dimethyl-hex-3-yne-2,5 bis-tertiary-butyl peroxide. The initiator isused in an amount of between about 0.005% and about 1% by weight basedon the weight of the reaction mixture solution. The grafting ispreferably carried out in an inert atmosphere, such as under nitrogenblanketing. The resulting polymer intermediate is characterized byhaving carboxylic acid acylating functions within its structure.

In the solid or melt process for forming a graft polymer, theunsaturated carboxylic acid with the optional use of a radical initiatoris grafted on molten ethylene copolymer rubber using rubber masticatingor shearing equipment. The temperature of the molten material in thisprocess may range from about 150° C. to 400° C.

Polymer substrates or interpolymers are available commercially.Particularly useful are those containing from about 40 to about 60 molepercent ethylene units, about 60 to about 40 mole percent propyleneunits. Examples are "Ortholeum 2052" and "PL-1256" available from E. I.du Pont de Nemours and Co. The former is a terpolymer containing about48 mole percent ethylene units, 48 mole percent propylene units and 4mole percent 1,4-hexadiene units, having an inherent viscosity of 1.35.The latter is a similar polymer with an inherent viscosity of 1.95. Theviscosity average molecular weights of the two are on the order of200,000 and 280,000, respectively.

The polymer intermediate possessing carboxylic acid acylating functionsis reacted with an amino-aromatic compound such as nitrophenylphenylenediamine represented by the following general formula ##STR2##in which R¹ is --NH₂, --CH₂ --(CH₂)_(n) --NH₂, --CH₂ -aryl-NH₂ in whichn has a value from 1 to 10, R² is hydrogen or a nitro group, and R³ ishydrogen or a nitro group.

Particularly preferred amino-aromatic compound isN-(2,4-dinitrophenyl)1,4-phenylenediamine.

The reaction between the polymer substrate intermediate having graftedthereon carboxylic acid acylating function and the prescribed compoundis conducted by heating a solution of the polymer substrate under inertconditions and then adding the compound to the heated solution generallywith mixing to effect the reaction. It is convenient to employ an oilsolution of the polymer substrate heated to 140° C. to 175° C. whilemaintaining the solution under a nitrogen blanket. The compound is addedto this solution and the reaction is effected under the notedconditions.

The novel grafted and derivatized polymers of the invention are usefulas an additive for lubricating oils. They are multifunctional additivesfor lubricants being effective in providing dispersancy, viscosity indeximprovement and antioxidant properties to lubricating oils. They can beemployed in a variety of oils of lubricating viscosity including naturaland synthetic lubricating oils and mixtures thereof. The novel additivescan be employed in crankcase lubricating oils for spark-ignited andcompression-ignited internal combustion engines. The compositions canalso be used in gas engines or turbines, automatic transmission fluids,gear lubricants, metal-working lubricants, hydraulic fluids, and otherlubricating oil and grease compositions. The base oils may be a naturaloil including liquid petroleum oils and solvent-treated or acid-treatedmineral lubricating oils of the paraffinic, naphthenic and mixedparaffinic-naphthenic types or synthetic or semisynthetic oils or blendsthereof with natural oils. In general, the lubricating oil compositionof the invention will contain the novel reaction product in aconcentration ranging from about 0.5 to 10.0 weight percent. A preferredconcentration range for the additive is from about 1 to 15 weightpercent based on the total weight of the oil composition. Oilconcentrates of the additives may contain from about 1 to 50 weightpercent of the additive reaction product in a carrier or diluent oil oflubricating oil viscosity.

The novel reaction product of the invention may be employed in lubricantcompositions together with conventional lubricant additives. Suchadditives may include additional dispersants, detergents, antioxidants,pour point depressants, antiwear agents, and the like.

The following examples illustrate the novel reaction product additive ofthe present invention and its use and properties.

EXAMPLE I

Twenty grams of solid maleic anhydride grafted ethylene-propylenepolymer (rubber) in which the polymer substrate consisted of about 60mole percent ethylene and 40 mole percent propylene having a numberaverage molecular weight of about 100,000 on which has been grafted 0.8weight percent of maleic anhydride was dissolved in 135 grams of solventneutral oil at 160° C. with mechanical stirring while the mixture wasmaintained under a nitrogen blanket. After the rubber polymer haddissolved, mixing was continued for an additional hour at 160° C. 0.62Gram of neat N-(2,4-dinitrophenyl) 1,4-phenylenediamine followed by 6.0grams of low molecular weight ethylene oxide polymer (Surfonic L-24-7manufactured by Texaco Chemical Co.) was added to the oil solution ofthe polymer and a reaction effected over three hours at 160° C. undernitrogen. The reaction mixture containing the derivatized graft polymerwas then cooled and filtered. FTIR showed quantitative conversion.

EXAMPLE II

The novel additive reaction product of the invention was tested for itseffectiveness as a dispersant and as an antioxidant.

The lubricating oil used in the dispersancy test was the typicalformulated lubricating oil illustrated below in Table 1.

                  TABLE 1                                                         ______________________________________                                        Parts by Weight Component                                                     ______________________________________                                        Solvent neutral oil A                                                                           75.25                                                       Solvent neutral oil B                                                                           21.64                                                       Zinc dialkyldithiophosphate                                                                     1.22                                                        4,4'Dinonyldiphenylamine                                                                        .39                                                         Overbased magnesium sulfonate                                                                   1.50                                                        Silicone antifoamant                                                                            150     ppm                                                 Product of Example I                                                                            10      (1.25 wt % polymer)                                 ______________________________________                                    

Oil A had asp. gr. 60°/60° F. of 0.858-0.868; Vis 100° F. 123-133; PourPoint 0° F. Oil B had asp. gr. 60°/60° F. of 0.871-0.887; Vis. 100° F.325-350; Pour Point +10° F. Zinc salt is a salt of mixedalcohols-isopropanol and P₂ S₅ product as described in U.S. Pat. No.3,292,181. The overbased magnesium sulfonate had a TBN of 395 and is asalt of a branched (C₂₀ -C₄₀) monoalkylbenzene sulfuric acid (MW530-540) together with about 10% magnesium carbonate, 14% magnesiumhydroxide and 4% magnesium sulfate.

The dispersant properties of the additive-containing oil are determinedin the Bench VE Dispersancy Test (BVET). Dispersancy of a lubricatingoil is determined relative to three references which are the resultsfrom three standard blends tested along with the unknown. The testadditives were blended into a formulated oil containing no dispersant.The additive reaction product was employed in the oil at a concentrationof 1.25 weight percent based on the total weight of the oil composition.As shown below in Table 2, the numerical value of the test resultsdecreases with an increase in effectiveness.

                  TABLE 2                                                         ______________________________________                                        BENCH VE DISPERSANCY TEST                                                                          Additive Result                                          ______________________________________                                        Example I               53                                                    Maleic anhydride grafted EPM                                                                         190                                                    Ethylene-Propylene Copolymer (EPM)                                                                   200                                                    ______________________________________                                    

EXAMPLE III

The antioxidant properties of the novel reaction product in alubricating oil were determined in the Bench Oxidation Test. In thistest, 1.5 weight percent of the additive reaction product is blendedinto solvent neutral oil (S.U.S. at 100° F. of 130). The mixture iscontinuously stirred while being heated accompanied by bubbling withair. Samples are withdrawn periodically for analysis by DifferentialInfrared Absorption (DIR) to observe changes in the intensity of thecarboxyl vibration band at 1710 cm-1. A low carboxyl vibration bandintensity indicates higher thermal-oxidative stability of the sample.

                  TABLE 3                                                         ______________________________________                                        BENCH OXIDATION TEST                                                                               Additive Result                                          ______________________________________                                        Example I              4.3                                                    Maleic anhydride grafted EPM                                                                         27.0                                                   Ethylene-Propylene Copolymer (EPM)                                                                   15.0                                                   ______________________________________                                    

The test result for Example III demonstrates substantial improvements inantioxidant properties due to incorporation of the novel reactionproduct of the invention in an oil composition as compared to theresults obtained from known VI and dispersant VI improvers.

What is claimed is:
 1. A derivatized graft copolymer prepared by thesteps comprising:(A) reacting a polymer prepared from ethylene and atleast one (C₃ -C₁₀) alpha-monoolefin and, optionally, a polyene selectedfrom non-conjugated dienes and trienes comprising from about 15 to 80mole percent of ethylene, from about 20 to 85 mole percent of said (C₃-C₁₀) alpha-monoolefin, and from about 0 to 15 mole percent of saidpolyene and having a number average molecular weight ranging from about5,000 to 500,000 with at least one olefinic carboxylic acid acylatingagent to form one or more acylating reaction intermediates characterizedby having a carboxylic acid acylating function within their structure;and (B) reacting said reaction intermediate in (A) with a nitrophenylphenylenediamine represented by the general formula ##STR3## in which R¹is --NH₂, --CH₂ --(CH₂)n--NH₂, --CH₂ -aryl-NH₂ in which n has a valuefrom 1 to 10, R² is hydrogen or a nitro group, and R³ is hydrogen or anitro group.
 2. A copolymer according to claim 1 wherein said polymerhas a number average molecular weight from about 25,000 to 250,000.
 3. Acopolymer according to claim 1 wherein said polymer has a number averagemolecular weight from about 50,000 to 150,000.
 4. A copolymer accordingto claim 1 wherein said polymer comprises from about 25 to 75 molepercent ethylene and from about 25 to 75 mole percent of at least one(C₃ -C₁₀) alpha-monoolefin and optionally, 0 to about 15 mole percent ofa polyene selected from non-conjugated dienes and trienes.
 5. Acopolymer according to claim 1 wherein said polymer comprises about 50to about 80 mole % ethylene, about 20 to about 50 mole % of at least one(C₃ -C₁₀) alpha-monoolefin and, optionally, 0 to about 15 mole percentof a polyene selected from non-conjugated dienes and trienes.
 6. Acopolymer according to claim 1 wherein said polymer comprises from about25 to 55 mole percent ethylene and from about 45 to 75 mole percent ofpropylene.
 7. A copolymer according to claim 4 wherein said polymercontains from about 0.1 to 10 mole percent of a polyene.
 8. A copolymeraccording to claim 1 wherein said olefinic carboxylic acid acylatingagent is maleic anhydride.
 9. A copolymer according to claim 1 whereinsaid olefinic carboxylic acid acylating agent is itaconic anhydride. 10.A copolymer according to claim 1 wherein said nitrophenylphenylenediamine is N-(2,4-dinitrophenyl) 1,4-phenylenediamine.
 11. Alubricating oil composition comprising a major amount of an oil oflubricating viscosity and a minor amount effective to impart viscosityindex improvement, dispersancy, and antioxidant properties to said oilof a reaction product prepared by the steps comprising:(A) reacting apolymer prepared from ethylene and at least one (C₃ -C₁₀)alpha-monoolefin and, optionally, a polyene selected from non-conjugateddienes and trienes comprising from about 15 to 80 mole percent ofethylene, from about 20 to 85 mole percent of said (C₃ -C₁₀)alpha-monoolefin, and from about 0 to 15 mole percent of said polyeneand having a number average molecular weight ranging from about 5,000 to500,000 with at least one olefinic carboxylic acid acylating agent toform one or more acylating reaction intermediates characterized byhaving a carboxylic acid acylating function within their structure, and(B) reacting said reaction intermediate in (A) with a nitrophenylphenylenediamine represented by the formula ##STR4## wherein R¹ is--NH₂, --CH₂ --(CH₂)n--NH₂, --CH₂ -aryl-NH₂ in which n has a value from1 to 10, R² is hydrogen or a nitro group, and R³ is hydrogen or a nitrogroup.
 12. The lubricating oil composition according to claim 11 whereinsaid polymer has an average molecular weight ranging from about 25,000to about 250,000.
 13. The lubricating oil composition according to claim11 wherein said polymer has an average molecular weight ranging fromabout 50,000 to about 150,000.
 14. The lubricating oil compositionaccording to claim 11 wherein said polymer comprises about 50 to about80 mole % ethylene, about 20 to about 50 mole % of at least one (C₃-C₁₀) alpha-monoolefin and, optionally, 0 to about 15 mole percent of apolyene selected from non-conjugated dienes and trienes.
 15. A copolymeraccording to claim 11 wherein said polymer comprises from about 25 to 55mole percent ethylene and from about 45 to 75 mole percent of propylene.16. A copolymer according to claim 11 wherein said polymer contains fromabout 0.1 to 10 mole percent of a polyene.
 17. The lubricating oilcomposition according to claim 11 wherein the ethylenically unsaturatedcarboxylic acid material is maleic anhydride.
 18. The lubricating oilcomposition according to claim 11 wherein the ethylenically unsaturatedcarboxylic acid material is itaconic anhydride.
 19. The lubricating oilcomposition according to claim 11 wherein said nitrophenylphenylenediamine is N-(2,4-dinitrophenyl)1,4-phenylenediamine.
 20. Aconcentrate for a lubricating oil comprising a diluent oil of lubricantviscosity and from about 1 to about 50 wt. % of the derivatized graftcopolymer compound of claim 1 based on the total weight of theconcentrate.